. >> reporter: despite all of those concerns, mark brown is now working with oil and gas companies that are fracking in pennsylvania. brownstein says the environmental group isn't in favor of fracking but it is in favor of using more natural gas as an alternative to coal because gas is cleaner. a new report by the environmental protection agency says that u.s. power plants have recently cut their total greenhouse gas emissions by more than 6%. mostly because so many have switched from coal to gas. brownstein believes natural gas is the fossil fuel we should be using until we get our energy from renewable resources like wind and solar power. >> that's what we want but we also understand that it's going to take some time to get there. and the question is, what do you do in the meantime? >> so a little over two years ago the environmental defense fund started to talk to the companies fracking for gas in pennsylvania. the ones that so many other environmentalists see as the enemy. >> and in order to make change, you have to take the time to learn their industry, learn their concerns and be